The two things I noticed about the second one (admittedly the only one I looked at) were the lack of shadows on the top couple of buildings and the overlap of shadows that gives rise to darker spots. The shadow overlap thing is no doubt the result of result of drop shadows on each entity rather than a whole layer.

I do agree with RPMiller about the curved thing. It looks like a pointy berm to me.

Overall, though, it's quite nice.